The committee set up by the power ministry to probe the recent grid collapse, which disturbed large parts of the country on two successive days, has recommended phasing out of the unscheduled interchange (UI) mechanism which allows state utilities to overdraw power from the grid by paying small fines.
The UI mechanism has virtually developed a parallel power market for state electricity boards which use the facility to meet power requirements beyond their allocated quotas.
As per the central electricity regulator?s tightened grid code, the permissible frequency band for grid operations is 49.5-50.2Hz. The UI rates range from 16 paise per MWh for frequencies above 50 Hz to R9 per MWh when frequency drops to 49.5 Hz, the lower end of the band. As FE reported earlier, states don?t even care to pay UI charges in time and most of them have huge unpaid UI balances.
The panel, which submitted its report to the power ministry late last week, attributed the two-day blackout to lack of grid discipline by all power sector participants. It said adherence to the grid code should be made mandatory with provisions for tough punitive measures for deviations.
?A review of the UI mechanism should be carried out in view of its impact on recent grid disturbances. Frequency control through UI may be phased out in a time-bound manner and generation reserves/ancillary services may be used for frequency control. An appropriate regulatory mechanism needs to be put in place for this purpose,? the report said. It also suggested amending the Electricity Act to strengthen penal action for violating the grid code and misusing the UI mechanism.
The committee headed by Central Electricity Authority chairperson AS Bakshi and including Power Grid Corporation CMD AM Nayak and Power System Operation Corporation CEO SK Soonee was set up immediately after the northern grid collapse of July 30 and northern, eastern and northeastern grid collapse of July 31.
Overdrawal and underdrawal of power from the grid by various states resulted in frequency disturbances, tripping lines and resulting in grid collapses, the panel said.
The panel has suggested that frequency control should be undertaken through generation reserves/ancillary services which eliminate the chance of states overdrawing from the grid as frequency is kept stable through system controls. It said this needs to be adopted as the current UI mechanism is sometimes ?endangering grid security?.
CERC chairperson Pramod Deo told FE that he was also in favour of winding up the UI mechanism.
On maintaining frequency stability, the committee proposed reducing the frequency band from the present 48.5-50.2 Hz range to closer to 50 Hz to check variations and prevent overdrawals. It also suggested modernising transmission lines, especially at the level of states, to manage congestion in the system better. It said audit of devices such as HVDC, TCSC, SVC and PSS should be done immediately to ensure their stability features are enabled.
As discussed earlier during the meeting with power secretary, the committee also favoured implementing islanding schemes for essential services like rail and hospitals so that even during a blackout, power supply could be maintained in these islands.
?As the national grid is on the horizon, homogenising system operation philosophy is the need of the hour. The present organisational set-up of load dispatch centres needs to be reviewed. System operation needs to be entrusted to an independent system operator. In addition, SLDCs should be reinforced and ring-fenced for ensuring functional autonomy,? the panel has said.
The committee has found bad communication set up between transmission utilities at central and state levels as a possible reason why grid discipline is often ignored. It has said setting up a dedicated telecom network between stations as mandatory condition before any new transmission network is approved by states. A new cyber protection cell has also been proposed to prevent the grid from any future cyber attack The committee, however, found that the present collapse had no indication of any such attack.
Sparking Change
* Plan outage better, review penal provisions
* Give more autonomy to load despatch centres
* Plan electricity islanding systems
* Improve planning and investment at state level
* Ensure better communication for despatch centres
* Shorten start-up time at generating stations
* Review transmission planning criteria